Effect of Humic Acid and Vermicompost on Some Vegetative Indices and Proline Content of Catharanthus roseous under Low Water Stress

To investigate the effect of vermicompost (0, 25, and 50%) and humic acid (0, 50, and 100 mg/l) on some traits of Catharanthus roseous under low water stress (50 and 100% field capacity), a factorial experiment based on a completely randomized design was conducted in 1399 at greenhouse conditions. Catharanthus roseous cuttings were grown in a light and moist medium containing peat moss and leaf mold with humic acid and vermicompost treatments. Then low water stress was applied for one month. The results showed that low water stress of 50% FC caused a significant decrease in vegetative indices, cell membrane, and plant pigment and increased proline. The maximum shoot fresh weight and root dry weight, flowers number, anthocyanin, and total chlorophyll were recorded in 100% FC + humic acid 100 mg/l treatment, and the highest shoot dry weight, root fresh weight, and membrane stability were obtained in 100% FC + 50% vermicompost treatment. The highest proline amount was obtained in 50% FC treatment and the lowest in 100% FC + humic acid 100 mg/l treatment. Therefore, according to the results, the use of vermicompost and humic acid can be recommended to reduce the negative effects of water stress in Catharanthus roseous.